Hi! I understand your One Calendar app is showing a "no internet connection" error and not syncing, even though you probably have internet access. Let’s work through this carefully to get your calendar syncing again.

First, just so I’m clear:
- Are you seeing this error only in One Calendar, or do other apps show internet issues too?
- Are you connected via Wi-Fi or wired network on your Windows 10 device?
- Have you tried restarting your device yet?

Here’s a straightforward plan to troubleshoot:

1. Verify internet connection:
- Make sure your device is connected properly to the internet by opening a web page in your browser.
- Turn off Wi-Fi temporarily and reconnect, just to reset the connection.

2. Check One Calendar’s permissions and network access:
- Since you're on Windows 10, ensure One Calendar has permission to use the internet. Go to Settings > Privacy > App permissions > Background apps and confirm One Calendar is allowed to run in the background.
- Also, check firewall settings: open Windows Defender Firewall and verify One Calendar isn’t blocked. Temporarily disable the firewall to test syncing.

3. Restart the One Calendar app:
- Close One Calendar completely, then reopen it.

4. Sign out and sign back in:
- Sometimes re-authenticating fixes sync issues. Sign out of your calendar account in One Calendar, then sign back in.

5. Remove and re-add your calendar account:
- Remove the connected calendar account (Google, Outlook, etc.) in One Calendar, then add it again. This can resolve token or authentication problems.

6. Check for updates:
- Ensure your Windows 10 and One Calendar app are up to date. Updates can fix bugs related to sync.

If these steps don’t work, there might be a deeper issue such as temporary server communication problems with One Calendar or sync limits reached (like the "too many requests" error reported sometimes with Microsoft 365 accounts). If it’s the latter, waiting a bit before trying again usually helps1.

By the way, can you confirm whether your other internet-based apps work fine? That helps isolate if this is app-specific or network-related.

Are you able to try these steps and let me know what happens? I’m here to keep helping!